Numerous researches have been carried out on concrete surface treatments in order to prevent the entrance of corrosive agents and moisture into concrete by imparting hydrophobicity to the concrete surface. Existing concrete surface treatments are largely divided into three approaches. The first existing concrete surface treatment approach is the use of hydrophobic pore liner that imparts hydrophobicity onto concrete surface. The second approach relies on pore blockers to block concrete pores. The pore blockers react with constituents in the concrete and forms insoluble products within the pores. The third is to apply a dense layer of high water resistance film onto the concrete surface. It has been found that treating concrete surface with one of the approaches alone does not give satisfactory results. For instance, pore liner modified concrete surfaces are found to be fragile without further protective means and can be washed off by water easily. In addition, pore liner has not been found effective in blocking water vapor and other gaseous corrosive agents, such as carbon dioxide. Pore blocking agents have similar problems. Although pore blockers can reduce water penetration, pore blockers penetrate into concrete porous surface less than pore liner, and pore blocker treated surfaces remain prone to carbon dioxide and other gaseous corrosive agents. Film-forming coats, very often, fail to be compatible with the concrete surface. Adhesion between existing polymeric coating with high water resistance and concrete has found to be weak and cannot withstand differential thermal expansion and contraction cycles of the concrete surfaces. The common solution to the above problems is to apply an additional primer layer as an interfacial enhancer between the concrete layer and the hydrophobicity treatment. However, application of the primer layer is time-consuming and expensive.
Silane is a well known surface coupling agent that can easily penetrate into concrete due to its inherent special chemical structures. Over the past 20 years, researchers have utilized silanes successfully to impregnate the concrete in depth. U.S. Pat. No. 4,716,051 discloses that the silane molecules can penetrate inside the concrete deeply by the use of alkyl trialkoxysilanes. In recent years, researchers have leveraged the reactivity of silane with suitable functional groups to polymerize with various monomers so as to form special polymer-based coating as silane-terminated polymer sealer on concrete. The incorporation of polymer groups combines the unique physical or chemical properties of polymer components and the inherent multifunctional properties of silane. Porsche et al. in U.S. Pat. No. 7,482,420 reports a method for making a silane-terminated polyurethane composition with high strength and high elongation. In U.S. Pat. No. 8,029,854, Johnston discloses a process for repairing concrete by using a silane-terminated pre-polymer polyurethane sealant. However, these coatings are associated with several disadvantages. Besides their complicated fabrication process, the silane-based polyurethane sealant is prone to react with water or moisture in concrete, leading to the expansion of coating.
Therefore, there is a need to provide a hydrophobicity surface treatment for concrete which is durable, effective in blocking water vapor and other gaseous corrosive agents without an additional application of primer layer and inert to water or moisture in concrete, in order to overcome the existing problems associated with conventional concrete surface treatment methods.
Citation or identification of any reference in this section or any other section of this application shall not be construed as an admission that such reference is available as prior art for the present application.